Sub Thresher's nuclear reactor remains buried at sea

The wreckage of USS Thresher more than 200 miles off the New England coast has never posed a threat to the environment, according to the U.S. Navy.

D. Allan Kerr

The wreckage of USS Thresher more than 200 miles off the New England coast has never posed a threat to the environment, according to the U.S. Navy.

Thresher (SSN 593) was the first nuclear submarine ever lost at sea. It sank during deep-diving tests in April 1963 following an overhaul at Portsmouth Naval Shipyard. With the loss of all 129 men aboard, the incident remains the worst submarine disaster the world has ever known.

Over the years since the tragedy, the Navy has visited the site on six occasions to monitor radioactivity in the area. The most recent testing was conducted in 1998. A 2011 report concluded the submarine "had no discernible effect of radioactivity" on the surrounding environment.

None of the six monitoring missions showed any evidence of radioactivity released from the submarine's nuclear reactor, said Thomas Dougan, spokesman for the Navy's Nuclear Propulsion Program.

"The reactor fuel elements are made of materials that are extremely corrosion resistant, even in seawater," Dougan stated recently. "The reactor could remain in seawater for centuries without releasing fission products."

In addition, the level of radioactivity "has decayed to a small fraction of what was present at the time of the sinking," according to Dougan. "Thus, there has been no need to perform another sampling mission since the 1998 monitoring."

The Navy has never considered salvaging the wreckage of the Thresher, according to Dougan.

"Attempting to raise sections of the ship would potentially result in further damage to them and could disturb the area," he said. "Additionally, the Navy considers the Thresher site to be a grave site and therefore not to be disturbed."

Once considered the most advanced naval vessel afloat, Thresher now lies in thousands of pieces on the ocean floor, about 8,400 feet below the ocean's surface.

According to the 2011 Navy report, the site was tested shortly after the fast-attack submarine sank, then again in 1965, 1977, 1983, 1986 and 1998.

A seventh expedition was headed by Dr. Robert Ballard in 1985. The renowned ocean explorer would admit nearly a quarter-century later that his widely publicized discovery of the ocean liner RMS Titanic was used as a cover story to check on the wreckage of Thresher and the submarine USS Scorpion for the Navy.

First search for Thresher

As the first nuclear submarine in history to be lost at sea, Thresher's tragic disappearance made headlines across the world in 1963, as did the massive sea hunt to find its remains. Initially, the search was fruitless.

Finally, in May the research ship Conrad dredged up small packages of O-rings — rubber rings used as washer-like seals for naval hydraulic equipment — including some that could have only come from Thresher. Two rubber gloves, oil samples and cork and plastic debris believed to be from the sub were recovered from the ocean as well.

The Conrad also used deep-water cameras to take photos of debris on the ocean floor, which according to searchers could have come from a Navy ship. These included a piece of broken pipe, metal plates and an air bottle standing upright on the ocean floor.

The Atlantis II, a research vessel from the Woods Hole Oceanographic Institute in Massachusetts, took samples from the sea bottom in that area, which showed no indication of radioactivity.

In a remarkable showing of consistency, Adm. Hyman Rickover, the legendary "father of the nuclear Navy," offered at that time the following statement, which half a century later would be echoed almost exactly:

"I can assure you there is no radioactive hazard as a result of this unfortunate accident," Rickover declared. "Reactors of the type used in the Thresher, as well as in all our nuclear submarines and surface ships, can remain submerged indefinitely in seawater without creating any hazard."

In June, the Navy's only bathyscaph — the Trieste — was employed to investigate the Thresher. According to Norman Polmar's book "The Death of the USS Thresher," the Italian-built vessel "was the world's only manned vehicle that could penetrate the 8,400-feet depths."

Trieste had already dived to 35,800 feet in June 1960 at the Marianas Trench — a record that stands to this day.

The bathyscaph — its name derived from the Greek words "bathy," meaning deep, and "scaphos," meaning boat or ship — was a two-man submersible. It consisted of a float chamber and then a smaller observation gondola attached underneath. The Trieste had been purchased by the Navy in 1958 for $250,000.

Home-ported in San Diego, Trieste was transported by ship to Boston via the Panama Canal. After several undersea attempts to locate Thresher, hampered repeatedly by adverse weather, the mechanical arm of Trieste retrieved a mangled 57-inch length of copper pipe on Aug. 28.

The pipe was presented at a press conference headed by Secretary of the Navy Fred Korth. Markings on the pipe, including the inscription "593 boat," verified it had come from the galley of the doomed submarine.

Lt. Cmdr. Donald Keach, the Trieste skipper, told reporters "the ocean floor in the area is like an automobile junk yard," according to Polmar's book.

No bodies were found, but the initial search for the Thresher was over.

Radioactive concerns

A 2011 Navy report with the rather unwieldy title "Environmental Monitoring and Disposal of Radioactive Wastes from U.S. Naval Nuclear-Powered Ships and Their Support Facilities" describes steps taken to gauge radioactivity at the site.

The report declares that in both 1963 and 1965, "radiation measurements, water samples, bottom sediment samples, and debris" from the wreckage were analyzed by "various laboratories."

Samples were tested from areas around both Thresher and Scorpion (SSN 589) — another nuclear submarine that sank in the Atlantic in 1968 — during subsequent years as well, according to the report.

"The reactor's many protective devices and inherent self-regulating features are designed to prevent any melting of the fuel elements," the report states. "Flooding of a reactor with seawater furnishes additional cooling for the fuel elements and so provides added protection against the release of radioactive fission products."

The radioactive isotope cobalt-60, used in the coolant systems of both submarines, was found in small doses within sediment samples in 1998, but not in surrounding water or marine life. The maximum concentration of cobalt-60 gauged at either site was 2.02 picocuries per gram, and most samples were much less.

"This is less than one-tenth the concentration of naturally occurring radioactivity in the sediment," according to the report issued by the Navy's Nuclear Propulsion Program.

A Navy investigation concluded a piping failure caused Thresher's nuclear reactor to shut down during sea trials. The powerless submarine then sank toward the ocean bottom and was crushed by enormous undersea pressure, investigators determined.

No cause for the Scorpion's loss has ever been determined.

A Titanic cover story

In 2008, Dr. Ballard — famed for his discovery of the Titanic shipwreck — revealed to the National Geographic Channel that he had investigated both sunken submarines for the Navy during that same expedition.

Ballard, a former active-duty Navy officer who retired as a commander in the Naval Reserve, admitted he used his search for the Titanic as a cover story to explore the Thresher and Scorpion wrecks as well. In return, the Navy funded Ballard's expedition.

He worked out a deal with the Navy allowing him to carry on his search for Titanic as time permitted, after he found the submarines. Ballard was secretly sworn back into active duty for the assignment.

Because of his updated equipment, Ballard was able to collect more precise data. The explorer found both reactors to be intact during his investigation. He also concluded that Scorpion had not been destroyed by hostile fire, as some had maintained.

Not only did Ballard's agreement with the Navy allow him to conduct a trial run of his equipment — especially the undersea robot sled Argo — but in searching for Thresher he came across the approach he later used to find Titanic.

Knowing the submarine had imploded under water pressure, Ballard operated his undersea camera in a side-to-side sweeping motion to find Thresher's path of debris instead of trying to pinpoint the vessel itself. This proved a time-saving and successful method. Believing Titanic must have imploded in a similar fashion, he used the same method to find the cruise ship shortly thereafter.

April 10 marks the 50th anniversary of the Thresher disaster. A privately funded 129-foot flagpole is being dedicated in Kittery, Maine, on April 7 as part of a permanent memorial to commemorate the historic tragedy.

D. Allan Kerr is a member of the Thresher Memorial Project Group. He may be reached at the_culling@hotmail.com.

Thresher memorial

What: Thresher Memorial Project Group is working to create a permanent tribute at Kittery's Memorial Circle

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